From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Boqun Feng <boqun.feng@gmail.com>,
Sasha Levin <sashal@kernel.org>,
frederic@kernel.org, quic_neeraju@quicinc.com,
joel@joelfernandes.org, josh@joshtriplett.org,
rcu@vger.kernel.org
Subject: [PATCH AUTOSEL 6.6 02/11] rcu-tasks: Repair RCU Tasks Trace quiescence check
Date: Sun, 24 Mar 2024 13:06:32 -0400 [thread overview]
Message-ID: <20240324170645.546220-2-sashal@kernel.org> (raw)
In-Reply-To: <20240324170645.546220-1-sashal@kernel.org>
From: "Paul E. McKenney" <paulmck@kernel.org>
[ Upstream commit 2eb52fa8900e642b3b5054c4bf9776089d2a935f ]
The context-switch-time check for RCU Tasks Trace quiescence expects
current->trc_reader_special.b.need_qs to be zero, and if so, updates
it to TRC_NEED_QS_CHECKED. This is backwards, because if this value
is zero, there is no RCU Tasks Trace grace period in flight, an thus
no need for a quiescent state. Instead, when a grace period starts,
this field is set to TRC_NEED_QS.
This commit therefore changes the check from zero to TRC_NEED_QS.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/rcupdate.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 44aab5c0bd2c1..f9173b972c7e2 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -189,9 +189,9 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
do { \
int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting); \
\
- if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
+ if (unlikely(READ_ONCE((t)->trc_reader_special.b.need_qs) == TRC_NEED_QS) && \
likely(!___rttq_nesting)) { \
- rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
+ rcu_trc_cmpxchg_need_qs((t), TRC_NEED_QS, TRC_NEED_QS_CHECKED); \
} else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
!READ_ONCE((t)->trc_reader_special.b.blocked)) { \
rcu_tasks_trace_qs_blkd(t); \
--
2.43.0
next parent reply other threads:[~2024-03-24 17:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240324170645.546220-1-sashal@kernel.org>
2024-03-24 17:06 ` Sasha Levin [this message]
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 03/11] rcu-tasks: Add data to eliminate RCU-tasks/do_exit() deadlocks Sasha Levin
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 04/11] rcu-tasks: Initialize " Sasha Levin
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 05/11] rcu-tasks: Maintain lists " Sasha Levin
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 06/11] rcu-tasks: Eliminate deadlocks involving do_exit() and RCU tasks Sasha Levin
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 07/11] rcu-tasks: Maintain real-time response in rcu_tasks_postscan() Sasha Levin
2024-03-24 17:06 ` [PATCH AUTOSEL 6.6 10/11] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() Sasha Levin
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